1. Field of the Invention
This invention relates to a film valve assembly, and more particularly to a film valve assembly for a heating, ventilation and air conditioning system.
2. Description of the Related Art
Referring to FIGS. 1 and 2, a heating, ventilation, and air conditioning system 1 disclosed in U.S. Pat. No. 6,616,060 is shown to include a housing 11, an evaporator 12 disposed in the housing 11, a heater 13 disposed in the housing 11, and a film valve assembly 2 disposed on the housing 11.
Referring to FIGS. 2 and 3, the film valve assembly 2 includes a frame 21 disposed on a housing 1, first and second roller mechanisms 22, 23 disposed respectively on two opposite sides of the frame 21, two tension rod units 24 disposed on the frame 21, and a film valve 25 having two ends 251 adhered respectively to the first and second roller mechanisms 22, 23. The frame 21 has a plurality of vent holes (not shown). The film valve 25 also has a plurality of vent holes 252.
The first roller mechanism 22 includes a mounting shaft 221 disposed fixedly on the frame 21, a rotating tube 222 sleeved rotatably on the mounting shaft 221, and a biasing member 223 for biasing the rotating tube 222 to rotate in a first direction. The second roller mechanism 23 is similar to the first roller mechanism 22 in construction except that the second roller mechanism 23 is biased to rotate in a second direction that is opposite to the first direction. Therefore, the film valve 25 is disposed between the first and second roller mechanisms 22, 23 under tension.
Referring to FIGS. 2 and 4, each of the tension rod units 24 includes two retaining members 241 made of a plastic material, and a tension rod 242. Each of the retaining members 241 has a shoulder 243, a skirt 244 press fitted within the tension rod 242, and a neck 245 inserted into a hole 212 in a sidewall 211 of the frame 21. During assembly, the skirt 244 is inserted into the tension rod 242. Subsequently, the neck 245 is inserted into the hole 212 in the sidewall 211. In this manner, the tension rods 242 are fixed to the frame 21 so as to permit extension of the film valve 25 between a base wall 210 of the frame 21 and the tension rods 242. However, it is difficult to insert the necks 245 of the retaining members 241 into the holes 212 in the sidewalls 211 during assembly. Furthermore, after assembly, the necks 245 of the retaining members 241 are prone to move within the holes 212 in the sidewalls 211. As a result, the tension rods 242 cannot be connected firmly to the frame 21. In addition, the film valve 25 is easily separated from the roller mechanisms 22, 23 due to the adhesive connection therebetween.